1. Field of the Invention
The present invention relates to a discharge valve assembly for restricting the discharge of compressed fluid in fluid machinery, and more particularly, to a discharge valve assembly of fluid machinery opened and closed in a sliding method, the discharge valve assembly for reducing fluid resistance during discharge of fluid and preventing back current of the discharged fluid.
2. Description of the Background Art
In general, fluid machinery sucks up fluid into a cylinder, compresses the fluid, and discharges the compressed fluid using a rotary motion or a linear motion of a piston combined with a driving motor. A discharge valve assembly for controlling discharge of fluid is included in the cylinder of the fluid machinery in almost cases.
A widely known discharge valve assembly includes a reed valve as shown in FIG. 1 and a piston valve as shown in FIG. 2.
The reed valve is formed so that one side end of a rectangular reed valve 1 is fixed to a cylinder or a valve plate 2 and that the other end that is a free end faces a discharge opening 2a formed on one side surface of the cylinder or the valve plate 2, to thus control discharge of the compressed fluid.
A retainer 3 for restricting the movement of the reed valve 1 is fixed to and combined with the reed valve 1 on the reed valve 1.
As shown in FIG. 2, the piston valve is formed so that a discharge opening 5a is formed on one side surface of the cylinder or a valve plate 5. A piston valve 4 having a predetermined weight is positioned above the discharge opening 5a. 
A valve housing 6 having an inner circumference slightly larger than the outer circumference of the piston valve 4 inside thereof so as to include the piston valve 4 and including a back current hole 6b formed on one side thereof for closing of the valve is fixedly combined with the one side surface of the cylinder or the valve plate 5 by a predetermined means such as a bolt.
However, the reed valve 1 has a shortcoming of causing valve noise while the reed valve 1 is opened and closed when a pressure ratio increases together with loss due to fluid resistance when fluid is discharged because the valve closes the discharge opening 2a. 
Also, in the piston valve 4, because the compressed fluid must be discharged while moving the heavy valve 4 upward, the fluid resistance is significant during the discharge of the compressed fluid. In particular, during a high-pressure ratio operation, while the piston valve 4 does not smoothly prevent the back current of the compressed fluid, loss due to the back current occurs. Also, during an abnormal operation, the piston valve 4 generates valve noise while going up and down in the valve housing 6 fixed to the cylinder or the valve plate 5.
Therefore, an object of the present invention is to provide a discharge valve assembly of fluid machinery, which is capable of reducing fluid resistance, reducing noise, and effectively preventing back current of fluid during the discharge of compressed refrigerant gas.
To achieve these and other advantages and in accordance with the purposes of the present invention, as embodied and broadly described herein, there is provided a discharge valve assembly of fluid machinery, comprising a valve housing connected to a discharge side of a compression chamber, forming a valve holding space for holding a valve, forming a discharge hole on one side of the valve holding space, forming a back current hole in the other side of the valve holding space to be separated from the discharge hole, and fixedly installed in a discharge chamber, and a sliding valve positioned between the discharge side of the compression chamber and the discharge hole of the valve housing so as to open and close the discharge hole while sliding according to the pressure of the compression chamber and the pressure of the discharge chamber and inserted into the valve holding space to slide.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.